1. Field of the Invention
High capacity freight cars such as well car, depressed center, and straight flat cars, large tank cars and other types for transporting heavy special equipment, use trucks of suitable carrying capacity often arranged for equalized design. Typical trucks, include Buckeye Elasto-Cushion six wheel (three axle) trucks and use a combination of side frames and equalizer arms that extend from the location of the central axle. The equalizer arms and side frame portions bear on cast steel boss blocks having male and female sets mounted on the side frames and equalizer arms. The invention uses a combination of features to achieve a composite boss block set having improved performance and service life.
2. Description of Related Art
The existing steel boss blocks cause wear on the side frames and equalizers as well as wearing themselves. Other plastic wear parts performing functions of original equipment steel rail car parts are known, such as coupler carrier wear plates, (U.S. Pat. No. 4,344,541 entitled xe2x80x9cCoupler carrier arrangement for railroad carsxe2x80x9d) center bearing liners (U.S. Pat. No. 4,075,951 entitled xe2x80x9cSelf lubricating center bearing linerxe2x80x9d) and brake beam guides (U.S. Pat. No. 4,480,721 entitled xe2x80x9cSnap-on slide bearing for recessed type guide lugs of unit brake beams.xe2x80x9d). These are cited as examples of the use of plastics, but do not contain the teachings of this specification for high load, mechanically fastened boss blocks. Their disclosures, however, are incorporated by reference as if fully set forth herein.
The AAR Manual of Standard and Recommended Practices Section D, Truck and Truck Details 8-300-95 at Page D-3, No. 23 covers these components and is incorporated by reference as if fully set forth herein.
The composite boss blocks of the invention may be made advantageously with a composite material that will prevent wear on faying surfaces as well as wear on themselves. The periodic build-up of contaminants and worn material and the need for replacement of the truck components causes mechanical inefficiency in the operation of the equipment and therefore a solution to this problem will prove very beneficial to the owners of cars using the three axle trucks.
The boss blocks of the invention are made from a new advanced bearing grade composite material sold under the trademark UltraComp. This material combines a proprietary thermoset plastic resin system with a synthetic fiber contained within the plastic matrix and is able to handle severe loads under impact and vibration. UltraComp remains self-lubricating throughout its bearing life. UltraComp is available from Tri-Star Plastics Corp. of 906 Boston Turnpike Shrewsbury Mass. 01545. A complementary wear pad can be used with, or in lieu of the composite boss block sets themselves.
The composite parts, formed and arranged as taught herein, and using the materials described, will reduce wear on interfacing surfaces of the truck at the location of the boss blocks. Relevant material properties of the preferred fiber reinforced resin are: Compressive Strength: 54,000 psi.; Coefficient of Friction on Steel:0.16, and Continuous Service Temperature: 260xc2x0 F.
The static vertical load on each composite boss block pair is about 50,000 lbs. producing a pressure of about 2,941 psi. Using a vertical dynamic load of 2 g., this provides a factor of safety of 8.5.
Related to the composite boss blocks is an approach using the same materials in a different configuration.